| 摘要 |
PURPOSE:To keep the light output of a semiconductor laser constant without knowing the temperature characteristics and the like of the semiconductor laser beforehand regardless of the characteristic fluctuation of the semiconductor laser due to ambient temperature and secular change, by providing an integrating circuit, which integrates the detected light output signals and uses the result for controlling the driving of the semiconductor laser. CONSTITUTION:An integrating circuit integrates the detected light output signals and uses the result for controlling the driving of a semiconductor laser. For example, the light output of a laser diode 54 is detected by a photodiode 11 and converted into an electric signals. The signals is amplified in an operation amplifier 13. The output from the amplifier is compared with a reference voltage Vf2 in a differential circuit 3 and the difference is obtained. After the differential voltages are integrated in an integrating circuit 4, a voltage, which drives the laser diode 54, is obtained in an output circuit 5. Thus the laser diode 54 emits the light. The light output is fed back to the light detecting circuit again. |
